The present invention is directed to a nickel pillared interlayered clay. More specifically, the present invention :s directed to a nickel pillared interlayered clay useful as a cataIytic agent in the hydrogenation of unsaturated edible oils. 2. Background of the Prior Art
Pillared interlayered clays are formed from naturally occurring and synthetic layered smectites. Of particular interest are the montmorillonite and laponite types of smectite layered silicates. These silicates may be visualized as "sandwiches" composed of silicate sheets containing four sheets of oxygen atoms. Smectites, especially montmorillonites and laponites, are synthesized into pillared interlayered clays by exchanging the cation in the natural silicate with a desired cationic species. This is accomplished by swelling the natural smectite in a suitable solvent, typically water, and adding the desired replacement cation to the suspension. Although aluminum cations are most commonly employed, the pillared interlayered clay formed by this process may be a nickel pillared interlayered clay, that is, the replacementation may be nickel cations.
This procedure results in the formation of a pillared interlayered clay because the cation introduced between clay platelets is more strongly attracted electrically than the cation naturally present in the smectite. Moreover, if the cation introduced into the smectite to form the pillared interlayered clay is catalytically active the so-formed pillared interlayered clay can be utilized as a catalyst.
The use of Group VIII noble metals and compounds containing Group VIII noble metals as hydrogenation catalysts is well known in the art. For example, the utilization of such Group VIII noble metals as palladium and platinum in this application is well established. It is known that a non-noble Group VIII metal, nickel, can also be used in the catalytic hydrogenation of unsaturated aliphatic compounds. Indeed, Israeli Patent Application 58,565, filed Oct. 25, 1979 and published Nov. 30, 1982, discloses a montmorillonite-based hydrogenation catalyst formed from a nickel pillared interlayered clay. That clay is utilized in the '565 application as a catalyst, in conjunction with a Group VIII noble metal, in the hydrogenation of the cycloalkene, cyclohexene, to form the cycloalkane, cyclohexane.
The catalyst of the '565 patent application is formed by the reaction of sodium hydroxide with nickel chloride in a water solution in which the nickel hydroxide precipitate is collected. The liquid is removed and the precipitate redispersed. This precipitate forms a hydrous sol and is aged for about 3 to 5 days. Thereupon, the sol is reacted with montmorillonite to form a nickel pillared interlayered clay.
Another nickel interlayered clay is disclosed by S. Yamanaka et al., Clays and Clay Minerals, 26 (1), 21 (1978). Yamanaka et al. describes several metal pillared interlayered clays of which nickel is an example. The nickel pillared interlayered clay of Yamanaka et al. is produced by mixing sodium hydroxide, nickel chloride and montmorillonite in water and allowing the solution to age at room temperature for 10 days. The filtered product of this reaction is a nickel pillared interlayered clay characterized by a ratio of hydroxyl groups, OH.sup.-, to nickel ions, Ni.sup.++, of between 0 and 2.0 on a molar basis. The nickel pillared interlayered clay of Yamanaka et al. is furthermore characterized by a "Q" value, the molar ratio of nickel, measured as nickel millimoles, to the clay ion exchange capacity, measured in milliequivalents of clay, of between 0 and 16.
Although the above disclosures represent advances in the art, still, the methods utilized in the formation of these nickel pillared interlayered clays cannot easily be commercially exploited due to the complexity of the methods used in their formation. Both methods require aging for several days. This processing step adds unacceptably long processing time. In addition, the clays produced in accordance with these procedures do not include as high a concentration of nickel to insure effective catalytic activity of the thus formed nickel pillared interlayered clay. In general, higher concentration of nickel in the clay, results in increased catalytic effect. Indeed, gas adsorption data establishes that surface area, pore volume and cyclohexane adsorption capacity of the nickel pillared interlayered clays of these teachings are not as high as that required to insure that they can be used in catalytic applications.
One particular hydrogenation reaction of considerable importance is the hydrogenation of unsaturated edible oils. The recent emphasis on reduction of serum cholesterol and the control of hyperlipidemia in general as a means of preventing heart disease has focused on the importance of unsaturated edible oils in a healthy diet. Of course, natural unsaturated oils must be hydrogenated to be ingestible. However, the degree of unsaturation of the hydrogenated oils is important not only in so far as edibility is concerned but, in addition, in order to insure that the oils do not contribute to increased blood vessel blockage. Surprisingly, recent studies have established that certain oils, having narrowly defined degrees of unsaturation, actually reduce blood vessel clogging in humans. Thus, there is a continuing need in the art to develop catalysts that can be used to form edible oils having the exact desired degree of unsaturation best suited to a healthy diet.
The above remarks establish the desirability of developing new and improved pillared interlayered clays which have particular application as catalysts in the hydrogenation of edible oils.